For a very long time various types of hydraulic machines have been known which rely on a rotating element provided with blades or vanes, the rotation driving force being generated by the pressure or displacement of a fluid discharged onto the blades or vanes by a distribution system.
However, none of these known types of hydraulic machines can exhibit at the same time a satisfactory energy efficiency at all rotation speeds in a range between zero speed and a relatively high speed.
Further, known hydraulic machines are relatively bulky as soon as the output power to be supplied is increased to relatively high levels.
Finally, these known machines all exhibit a certain inertia, which prevents their use in applications where instantaneous starting and stopping are required.